1. Field of the Invention
The present invention relates to a photovoltaic panel and a method of producing a photovoltaic panel.
2. Discussion of Related Art
Japanese patent document No. 7(1995)-335925 discloses a photovoltaic panel including (a) a transparent, plate-like member including a plurality of photovoltaic elements each of which has a P-N junction between its core portion and its shell portion; (b) a first electrode which is provided on one of opposite sides of the plate-like member and which is electrically connected to the respective shell portions of the photovoltaic elements; and (c) a second electrode which is provided on the other side of the plate-like member and which is electrically connected to the respective core portions of the photovoltaic elements.
The photovoltaic panel disclosed in the above-indicated document receives light on the above-indicated other side of the plate-like member where the second electrode does not fully cover the plate-like member. Since the second electrode does not fully cover a light receiving surface of the plate-like member, light can be incident to the light receiving surface of the plate-like member.
However, the photovoltaic panel disclosed in the above-indicated document has the problem that the second electrode only partly covers the light receiving surface of the plate-like member, i.e., that the light receiving area of the panel is decreased by the provision of the second electrode and accordingly the light incident to the panel cannot be efficiently utilized by the panel.
Japanese patent document No. 7(1995)-335925, indicated above, discloses a photovoltaic-panel producing method including (a) a photovoltaic-element-holding-member forming step of forming a light-transmitting, plate-like member holding a number of photovoltaic elements and (b) an electrode forming step of forming electrodes which are electrically connected to the photovoltaic elements held by the photovoltaic-element holding member formed in the photovoltaic-element-holding-member forming step. In the photovoltaic-element-holding-member forming step of the photovoltaic-panel producing method, the photovoltaic-element holding member is produced by first applying a light-transmitting resin to the photovoltaic elements fixed at respective predetermined positions on a substrate and subsequently curing the resin.
It is therefore an object of the present invention to make it possible to utilize more efficiently light incident to a photovoltaic panel.
It is another object of the present invention to make it possible to produce more easily a photovoltaic-element holding member than the photovoltaic-panel producing method disclosed in the above-indicated document does.
The above object may be achieved according to any one of the following features of the present invention in the form of a photovoltaic panel and a photovoltaic-panel producing method. Each of the following features of the present invention is numbered like the appended claims and depends from the other feature or features, where appropriate, to indicate and clarify possible combinations of technical features. It is to be understood that the present invention is not limited to the technical features or any combinations thereof that will be described for illustrative purposes only. It is to be further understood that a plurality of elements included in any one of the following features of the invention are not necessarily provided all together, and that the invention may be embodied without some of the elements described with respect to each feature.
(1) A method of producing a photovoltaic panel, comprising the steps of:
producing a light-transmitting, photovoltaic-element holding member which holds, along a reference surface, a plurality of photovoltaic elements each of which includes a P-type layer and an N-type layer, and
forming, on one of opposite sides of the photovoltaic-element holding member, a first electrode which is electrically connected to the respective P-type layers of the photovoltaic elements, and a second electrode which is electrically connected to the respective N-type layers of the photovoltaic elements. The reference surface may be a plane surface or a curved surface. The photovoltaic-element holding member may have a generally plate-like shape.
In the photovoltaic-panel producing method according to this feature, the photovoltaic-element holding member holding the photovoltaic elements is produced, and both the first electrode electrically connected to the P-type layers and the second electrode electrically connected to the N-type layers are provided on one of opposite sides of the holding member. That is, neither of the first and second electrodes is provided on the other side of the holding member. Therefore, in the case where the holding member has a light receiving surface on the other side thereof, the photovoltaic panel can efficiently utilize the light incident thereto, without needing to decrease the light receiving area thereof.
(2) A method according to the first feature (1), wherein the step of producing comprises
producing a light-transmitting member which has, along the reference surface, a plurality of photovoltaic-element holding portions, and
holding, with the photovoltaic-element holding portions, the photovoltaic elements, respectively.
The photovoltaic-element holding portions may comprise recesses which are formed in a photovoltaic-element holding surface of a photovoltaic-element holding plate, and those recesses may be formed either mechanically using, e.g., a drill, or chemically.
The photovoltaic-element holding portions may be provided at a predetermined, regular interval of distance. If the distance between each pair of holding portions adjacent to each other is too great, a density of the photovoltaic elements may be too low; and if the distance is too small, a power-generating efficiency of each photovoltaic element may be too low. Thus, the distance is predetermined in view of those factors.
An adhesive may be used to fix the photovoltaic elements to the photovoltaic-element holding portions. In this case, the adhesive is one which can transmit light in its cured state. Alternatively, the photovoltaic elements may be fitted in, and fixed to, the photovoltaic-element holding portions. In the latter case, it is preferred that receiving holes as the holding portions have a size which is somewhat smaller than that of the photovoltaic elements.
(3) A method according to the first or second feature (1) or (2), the step of producing comprises
forming a light-transmitting layer of a light-transmitting material before curing,
embedding at least respective portions of the photovoltaic elements in the light-transmitting layer, and
curing the light-transmitting layer in a state in which the at least respective portions of the photovoltaic elements are embedded in the light-transmitting layer.
In the photovoltaic-panel producing method according to this feature, the light-transmitting layer is formed, and subsequently at least respective portions of the photovoltaic elements are embedded in the light-transmitting layer. Then, the light-transmitting layer is cured to form the photovoltaic-element holding member.
The light-transmitting layer before curing has physical properties which assure that respective portions of the photovoltaic elements are embedded in the layer, in other words, properties which maintain the state in which the respective portions of the photovoltaic elements are embedded in the layer. In many cases, the light-transmitting layer is in a half-solid (or gel) state, but in some cases, it is in a liquid state. That the light-transmitting layer is in a state in which the photovoltaic elements can be embedded therein may be expressed in terms of a viscosity, or an elasticity, of the light-transmitting layer.
The light-transmitting layer needs to have physical properties which assure that respective portions of the photovoltaic elements are embedded therein, just at the time when the embedding step is carried out. However, when the light-transmitting layer is initially formed, the layer may have other physical properties. For example, the layer which has just been formed may have so low a viscosity that the layer cannot maintain a state in which respective portions of the photovoltaic elements are embedded therein.
When the light-transmitting layer in a state in which respective portions of the photovoltaic elements are embedded therein is cured, the layer can hold the photovoltaic elements. If at least respective portions of the photovoltaic elements are embedded in the layer, the layer can hold the elements. The photovoltaic elements may be entirely embedded in the layer. However, if the elements are not entirely embedded and are partly exposed, the electrodes can be formed easily.
(4) A method according to the third feature (3), wherein the step of embedding comprises
temporarily holding, with a temporarily holding surface of a temporarily holding member, the photovoltaic elements, and
moving the temporarily-holding member holding the photovoltaic elements, toward the light-transmitting layer, till the respective portions of the photovoltaic elements are embedded in the light-transmitting layer.
In the photovoltaic-panel producing method according to this feature, the temporarily holding surface of the temporarily holding member holds the photovoltaic elements, and the temporarily-holding member holding the photovoltaic elements is moved toward the light-transmitting layer, so that at least respective portions of the photovoltaic elements are embedded in the light-transmitting layer. That is, the photovoltaic elements are embedded in the light-transmitting layer, not directly, but indirectly using the temporarily-holding member. In some cases, the photovoltaic elements can be more easily embedded in the light-transmitting layer before curing, if the elements are temporarily held by the temporarily holding surface of the temporarily holding member, than if the elements are directly embedded at respective predetermined positions (or in a predetermined pattern) in the light-transmitting layer.
In addition, since the temporarily holding member is used, an amount of projection of each of the photovoltaic elements can be changed. For example, the amount of projection of each photovoltaic element can be selected at the least possible amount that can allow the formation of the electrodes. The amount of projection of each of the photovoltaic elements may be selected at a predetermined amount, irrespective of the shape or size of the each element.
If the temporarily holding member is provided by a flat member, the member can be easily operated. However, it is not essentially needed that the temporarily holding member be provided by a flat member. Similarly, the temporarily holding surface may be a plane surface or a curved surface.
In the case where the light-transmitting layer is formed of a photosetting or photocurable material and is cured by light incident to the temporarily holding member, the temporarily holding member is preferably formed of a light-transmitting material. On the other hand, in the case where the light-transmitting layer is formed of a thermosetting material and is heated by heat applied to the temporarily holding member, the temporarily holding member is preferably formed of a material which is excellent to heat transfer. In many cases, the light-transmitting layer can be more easily cured or set by heat applied, or light incident, to the temporarily holding member.
When the photovoltaic elements are temporarily adhered to a plate-like holding member, an adhesive such as an adhesive sheet may be utilized. Preferably, the adhesive has a lower adhesiveness to the photovoltaic elements than its adhesiveness to the light-transmitting layer. In the latter case, when the plate-like member is removed from the light-transmitting layer after the layer is cured to hold the elements, the elements are prevented from coming off the layer.
(5) A method according to the fourth feature (4), wherein the step of moving comprises pressing, in a state in which the photovoltaic elements contact the light-transmitting layer, the temporarily-holding member and the light-transmitting layer against each other.
Since the temporarily-holding member and the light-transmitting layer pressed against each other, the photo photovoltaic elements can be surely embedded in the light-transmitting layer.
(6) A method according to any one of the third to fifth features (3) to (5), wherein the step of forming the light-transmitting layer comprises supplying the light-transmitting material to a container and thereby forming the light-transmitting layer.
In many cases, the light-transmitting layer is formed of a material in a liquid or half-solid state. Accordingly, the layer can be easily formed using the container.
Usually, the container is one that is used for just forming the light-transmitting layer and is not employed as part of the photovoltaic panel. Therefore, after the photovoltaic-element holding member is produced, or after the photovoltaic panel is produced, the container is removed. However, the container may be employed as part of the photovoltaic panel.
In the case where at least a portion of the container is formed of a light-transmitting material, that portion of the container need not be removed. That is, that portion of the container can be deemed as part of the light-transmitting layer, and a rigidity of the photovoltaic panel can be increased by that portion of the container.
In the case where the container is removed after the photovoltaic panel is produced, the container can be used to protect the light-transmitting layer during the production of the panel.
As will be described in DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS, a portion of the container may be utilized as a stopper which defines a limit of movement of the temporarily holding member toward the container.
The container is not essentially needed to form the light-transmitting layer. For example, if the light-transmitting layer is formed of a material having a high viscosity, the container is not needed.
(7) A method according to the first feature (1), wherein the step of producing comprises
arranging, according to a predetermined rule, a plurality of transparent spherical members, along a reference plane, and
holding, with the arranged spherical members, the photovoltaic elements, such that the photovoltaic elements are positioned on the spherical members.
The transparent spherical members may be positioned at respective vertices of a triangle or a rectangle, as shown in FIG. 25 or FIG. 26, respectively, and respective positions of the photovoltaic elements are determined by the respective positions of the spherical members. In the example shown in FIG. 25, each photovoltaic element is supported by three spherical members; and, in the example shown in FIG. 26, each photovoltaic element is supported by four spherical members. The photovoltaic panel (i.e., closest packing) shown in FIG. 25 in which each photovoltaic element is supported by three spherical members enjoys a higher density of photovoltaic elements than that shown in FIG. 26.
Since the spherical members are arranged along a reference plane, i.e., in a single layer, respective positions of the photovoltaic elements are determined by the spherical members. That is, the photovoltaic elements can be positioned at respective desirable positions by selecting the size of the spherical members or the pattern in which the spherical members are positioned.
Preferably, the spherical members are formed of an optical ceramics or an optical resin. In addition, preferably, the spherical members have a higher strength than the photovoltaic elements, but this feature is not essentially needed.
For example, the photovoltaic-element holding member may be produced by first using the spherical members to hold the photovoltaic elements, casting a material before curing, a and then curing the material. Preferably, the material before curing has a lower viscosity than that of the light-transmitting material.
(8) A method according to any one of the fourth to seventh features (4) to (7), wherein the temporarily-holding member is formed of an elastic material, and wherein the step of temporarily holding comprises stretching the temporarily-holding member holding the photovoltaic elements, to change a space between each pair of adjacent photovoltaic elements of the plurality of photovoltaic elements.
The space between each pair of photovoltaic elements adjacent to each other can be increased by stretching the temporarily holding member. An amount of increasing of the space can be changed by changing an amount or proportion of stretching of the temporarily holding member.
For example, in the case where the temporarily holding member holds the photovoltaic elements such that there remains substantially no space between each pair of adjacent photovoltaic elements, a space is produced between each pair of adjacent photovoltaic elements, by stretching the temporarily holding member. In many cases, arranging the photovoltaic elements such that there remains substantially no space between each pair of adjacent photovoltaic elements, is easier than arranging the elements such that there remains a predetermined space between each pair of adjacent elements, and the photovoltaic elements arranged in the former manner enjoys a higher density than those arranged in the latter manner.
The temporarily holding member can be stretched in one direction only, or in each of two directions that intersect each other, preferably, two directions that are perpendicular to each other.
(9) A photovoltaic panel, comprising:
a plurality of photovoltaic elements each of which includes a P-type layer and an N-type layer;
a first electrode which is provided on one of opposite sides of a first plane intersecting the photovoltaic elements and which is electrically connected to the respective P-type layers of the photovoltaic elements;
a second electrode which is provided on the one of the opposite sides of the first plane and which is electrically connected to the respective N-type layers of the photovoltaic elements; and
a light-transmitting layer which is formed of a light-transmitting material and which is provided on the other side of the first plane and which fills at least a space between the first plane and a second plane which is parallel to the first plane and is tangent to the photovoltaic elements.
In the photovoltaic panel according to this feature, both the first and second electrodes are formed on one of opposite sides of a first plane that intersects the photovoltaic elements, and the light-transmitting layer is formed on the other side of the plane. The light-transmitting layer is formed of a light-transmitting material which fills a space between the first plane and a second plane which is tangent to the photovoltaic elements. Thus, neither of the first and second electrodes are provided on the opposite side on which the light-transmitting layer is provided. Therefore, if light is incident to the light-transmitting layer, the photovoltaic panel can efficiently utilize the light incident thereto, without needing to decrease its light receiving area.
The material used to form the light-transmitting layer may be an optical ceramics or an optical resin. Preferably, the material is excellent with respect to light transmittance and is free of yellowing. More preferably, the material is excellent with respect to weather resistance, chemical resistance, and electrical insulation, and has a mechanical strength higher than a certain degree. More preferably, the material is excellent with respect to moldability or formability. The material may be toughened glass, acrylic resin, urethane resin, polycarbonate resin, or unsaturated-polyester resin.
Since the photovoltaic elements are held by the light-transmitting layer, the light-transmitting layer may be called as a photovoltaic-element holding layer.
(10) A photovoltaic panel according to the ninth feature (9), wherein the first plane divides each of the photovoltaic elements into a first portion whose volume is smaller than 50% of a volume of the each photovoltaic element, and a second portion whose volume is greater than 50% of the volume, and wherein the light-transmitting layer is provided on the other side of the first plane on which the respective second portions of the photovoltaic elements are located.
The more portions of the photovoltaic elements are embedded in the light-transmitting layer, the less likely the elements are to come off the layer. In view of this, it is desirable that the more portions of the photovoltaic elements be embedded. More specifically described, it is preferred that not less than 45%, 50%, 55%, 60%, 65%, or 70% of each photovoltaic element be embedded in the light-transmitting layer.
Electric power is generated at the P-N junction of each photovoltaic element. In the case where light is incident to respective portions of the respective P-N junctions of the photovoltaic elements that are embedded in the light-transmitting layer, and electric power is generated at those portions, it is preferred that more portions of the P-N junctions be embedded in the layer.
However, it cannot be said in all cases that the more portions of the P-N junctions are embedded, the more efficiently the electric power is generated. How effectively the photovoltaic elements are embedded depends on the direction in which light is incident to the photovoltaic panel, and/or the shape of the photovoltaic elements. When light is incident to the photovoltaic panel in a certain direction or directions, a portion of each photovoltaic element may be shaded by another portion of the same. In the case where each photovoltaic element has a generally spherical shape and somewhat more than 50% of the each element is embedded in the light-transmitting layer, at least half the each element can be utilized to generate electric power, irrespective of which side of the photovoltaic panel the light may be incident to.
In order to form the electrodes, it is required that some portion of each photovoltaic element remain not embedded in the light-transmitting layer. In view of this, it is preferred that not more than 60%, 65%, 70%, 75%, or 80% of each photovoltaic element be embedded in the layer.
(11) A photovoltaic panel according to the ninth or tenth feature (9) or (10), wherein the light-transmitting layer has a shape having two plane surfaces parallel to each other, and wherein one of the two plane surfaces is substantially parallel to the first plane and the other plane surface is substantially parallel to the second plane.
According to this feature, since the light-transmitting layer has a generally flat shape, the photovoltaic panel can be used with ease.
In addition, since the light receiving surface may be provided by a plane surface, the light is prevented from being scattered by the light receiving surface.
Moreover, an angle of incidence of the light to the photovoltaic panel can be easily changed.
(12) A method of producing a photovoltaic panel, comprising the steps of:
producing a light-transmitting, photovoltaic-element holding member which holds a plurality of photovoltaic elements along a reference surface, and
forming at least one electrode which is electrically connected to the photovoltaic elements held by the photovoltaic-element holding member,
wherein the step of producing comprises
forming a light-transmitting layer of a light-transmitting material before curing,
embedding at least respective portions of the photovoltaic elements in the light-transmitting layer, and
curing the light-transmitting layer in a state in which the at least respective portions of the photovoltaic elements are embedded in the light-transmitting layer.
In the photovoltaic-panel producing method according to this feature, the light-transmitting layer is formed of a light-transmitting material before curing, and respective portions of the photovoltaic elements are embedded in the light-transmitting layer. Then, the light-transmitting layer is cured to produce a photovoltaic-element holding member. The present method can more easily produce the photovoltaic-element holding member than the conventional method in which, after a light-transmitting resin is applied to photovoltaic elements, the resin is cured.
The light-transmitting layer before curing has physical properties which allow respective portions of the photovoltaic elements to be embedded therein, that is, properties which maintain a state in which respective portions of the photovoltaic elements are embedded therein. It can also be said that the light-transmitting layer before curing has physical properties which assure that the layer is deformed while keeping close contact with the photovoltaic elements. Because of the physical properties of the light-transmitting layer, the layer behaves like a fluid (i.e., is deformed) and respective portions of the photovoltaic elements can be embedded in the layer. In many cases, the light-transmitting layer is in a half-solid (or gel) state, but in some cases, it is in a liquid state. That the light-transmitting layer is in a state in which the photovoltaic elements can be embedded therein may be expressed in terms of a viscosity, or an elasticity, of the light-transmitting layer.
The light-transmitting layer needs to have physical properties which assure that respective portions of the photovoltaic elements are embedded therein, just at the time when the embedding step is carried out. However, when the light-transmitting layer is initially formed, the layer may have other physical properties. For example, the layer which has just been formed may have so low a viscosity that the layer cannot maintain a state in which respective portions of the photovoltaic elements are embedded therein.
When the light-transmitting layer is cured in a state in which respective portions of the photovoltaic elements are embedded therein, the layer can hold the photovoltaic elements. If at least respective portions of the photovoltaic elements are embedded in the layer, the layer can hold the elements.
(13) A method according to the twelfth feature (12), wherein the step of embedding comprises embedding more than 50% of a volume of each of the photovoltaic elements, in the light-transmitting layer.
The more portions of the photovoltaic elements are embedded in the light-transmitting layer, the less likely the elements are to come off the layer. In view of this, it is desirable that the more portions of the photovoltaic elements be embedded. More specifically described, it is preferred that not less than 45%, 50%, 55%, 60%, 65%, or 70% of each photovoltaic element be embedded in the light-transmitting layer. In order to form the electrodes, it is required that some portion of each photovoltaic element remain not embedded in the light-transmitting layer. In view of this, it is preferred that not more than 60%, 65%, 70%, 75%, or 80% of each photovoltaic element be embedded in the layer.
(14) A method according to the twelfth or thirteenth feature (12) or (13), wherein the step of embedding comprises embedding more than 50% of an area of junction of a P-type layer and an N-type layer of each of the photovoltaic elements, in the light-transmitting layer.
(15) A method according to any one of the twelfth to fourteenth features (12) to (14), wherein the step of embedding comprises embedding, in the light-transmitting layer, the photovoltaic elements such that an electric-power generating efficiency per unit area of the photovoltaic panel is higher than a predetermined value.
Electric power is generated at the P-N junction of each photovoltaic element. In the case where light is incident to respective portions of the respective P-N junctions of the photovoltaic elements that are embedded in the light-transmitting layer, and electric power is generated at those portions, it is preferred that more portions of the P-N junctions be embedded in the layer.
However, it cannot be said in all cases that the more portions of the P-N junctions are embedded, the more efficiently the electric power is generated. How effectively the photovoltaic elements are embedded depends on the direction in which light is incident to the photovoltaic panel, and/or the shape of the photovoltaic elements. When light is incident to the photovoltaic panel in a certain direction or directions, a portion of each photovoltaic element may be shaded by another portion of the same. In the case where electric power is generated by light incident through the light-transmitting layer and each photovoltaic element has a generally spherical shape, it is preferred that somewhat more than 50% of the each element be embedded in the light-transmitting layer.
(16) A method according to any one of the twelfth to fifteenth features (12) to (15), wherein the step of curing comprises at least one of heating the light-transmitting layer, cooling the light-transmitting layer, and exposing the light-transmitting layer to light.
The material used to form the light-transmitting layer is cured after the photovoltaic elements are embedded therein. Some materials are heated for curing; some materials are cooled for curing; and other materials are exposed to light, such as ultraviolet rays or light containing ultraviolet rays, for curing.
The materials that are cured by heating are, e.g., thermosetting resins; the materials that are cured by cooling are, e.g., glass; and the materials that are cured by light are, e.g., photocurable resins (or photosensitive resins). In each case, it is preferred that the material be excellent with respect to not only light transmittance but also heat resistance and weather resistance.
The thermosetting resins are, e.g., UV-curable acrylic resins or UV-curable urethane resins.
(17) A method according to any one of the twelfth to sixteenth features (12) to (16), wherein the step of embedding comprises
temporarily holding, with a temporarily holding surface of a temporarily holding member, the photovoltaic elements,
moving the temporarily-holding member holding the photovoltaic elements, toward the light-transmitting layer, till the respective portions of the photovoltaic elements are embedded in the light-transmitting layer.
In the producing method according to this feature, the temporarily holding surface of the temporarily holding member holds a number of photovoltaic elements, and the temporarily-holding member holding the photovoltaic elements is moved toward the light-transmitting layer, so that respective portions of the photovoltaic elements are embedded in the light-transmitting layer. That is, the photovoltaic elements are embedded in the light-transmitting layer, not directly, but indirectly using the temporarily-holding member. In some cases, the photovoltaic elements can be more easily embedded in the light-transmitting layer before curing, if the elements are temporarily held by the temporarily holding surface of the temporarily holding member, than if the elements are directly embedded at respective predetermined positions (or in a predetermined pattern) in the light-transmitting layer.
If the temporarily holding member is provided by a flat member, the member can be easily operated. However, it is not essentially required that the temporarily holding member be provided by a flat member. Similarly, the temporarily holding surface may be either a plane surface or a curved surface.
In the case where the light-transmitting layer is formed of a photocurable material and is cured by light incident to the temporarily holding member, the temporarily holding member is preferably formed of a light-transmitting material. On the other hand, in the case where the light-transmitting layer is formed of a thermosetting material and is heated by heat applied to the temporarily holding member, the temporarily holding member is preferably formed of a material which is excellent to heat transfer. In many cases, the light-transmitting layer can be more easily cured or set by heat applied, or light incident, to the temporarily holding member.
(18) A method according to the sixteenth feature (16), wherein the step of temporarily holding comprises temporarily fixing the photovoltaic elements to an adhesive layer which is formed on the temporarily holding surface of the temporarily holding member.
The adhesive layer needs to hold just temporarily the photovoltaic elements, and need not hold the same for a long time. The adhesive layer is, e.g., a transparent adhesive sheet.
(19) A method according to the seventeenth or eighteenth feature (17) or (18), wherein the step of temporarily holding comprises temporarily holding, with an arranging member, the photovoltaic elements on the temporarily holding surface of the temporarily holding member.
Since the arranging member is used, the photovoltaic elements can be positioned at respective desired positions on the temporarily holding surface of the temporarily holding member. In addition, the arranging member may be used to define a distance between each pair of photovoltaic elements adjacent to each other.
The arranging member may be one which has a number of openings.
(20) A method according to the seventeenth or eighteenth feature (17) or (18), wherein the temporarily-holding member is formed of an elastic material, and wherein the step of temporarily holding comprises stretching the temporarily-holding member holding the photovoltaic elements, to change a space between each pair of adjacent photovoltaic elements of the plurality of photovoltaic elements.
The space between each pair of photovoltaic elements adjacent to each other can be increased by stretching the temporarily holding member. An amount of increasing of the space can be changed by changing an amount or proportion of stretching of the temporarily holding member.
For example, in the case where the temporarily holding member holds the photovoltaic elements such that there remains substantially no space between each pair of adjacent photovoltaic elements, a space is produced between each pair of adjacent photovoltaic elements, by stretching the temporarily holding member. In many cases, arranging the photovoltaic elements such that there remains substantially no space between each pair of adjacent photovoltaic elements, is easier than arranging the elements such that there remains a predetermined space between each pair of adjacent elements, and the photovoltaic elements arranged in the former manner enjoys a higher density than those arranged in the latter manner.
The temporarily holding member may be stretched in one direction only, or in each of two directions that intersect each other, preferably, two directions that are perpendicular to each other.
(21) A method according to the twentieth feature (20), wherein the step of moving the temporarily-holding member comprises moving the temporarily-holding member toward the light-transmitting layer, while preventing contraction of the temporarily-holding member stretched.
In the case where the temporarily-holding member is provided by an elastic member which is not plastically deformed when being stretched by an external force, i.e., which is used within a range of elastic deformation, the temporarily-holding member contracts because of its elastic force, if the external force is removed. Hence, the temporarily-holding member is kept stretched to prevent its contraction.
(22) A method according to any one of the seventeenth to twenty-first features (17) to (21), wherein the step of temporarily holding comprises
arranging, in a container, the photovoltaic elements into a single layer such that the photovoltaic elements contact with each other, and
pressing the temporarily holding member against the photovoltaic elements arranged in the single layer in the container.
For example, if the photovoltaic elements are supplied to the container which is being vibrated, the spaces among the photovoltaic elements can be reduced and can be easily packed such that there is substantially no space between each pair of adjacent photovoltaic elements. In the photovoltaic-panel producing method according to this feature, the density of the photovoltaic elements held by the temporarily holding member can be easily increased.
(23) A method according to any one of the seventeenth to twenty-second features (17) to (22), wherein the step of moving comprises pressing, in a state in which the photovoltaic elements contact the light-transmitting layer, the temporarily-holding member and the light-transmitting layer against each other.
When the temporarily-holding member and the light-transmitting layer are pressed against each other, the photovoltaic elements can be easily forced into the light-transmitting layer. To this end, it is preferred to employ a stopper which defines a limit of movement of the temporarily-holding member and the light-transmitting layer toward each other. In the latter case, it is possible to embed appropriately the photovoltaic elements in the light-transmitting layer.
Meanwhile, it is possible to carry out concurrently the curing step and the pressing step. In the case where the light-transmitting layer is cured slowly, the photovoltaic elements can be embedded in the light-transmitting layer being cured.
(24) A method according to any one of the seventeenth to twenty-third features (17) to (23), wherein the step of producing further comprises removing, after the step of curing, the temporarily holding member from the light-transmitting layer cured.
After the light-transmitting layer is cured, the temporarily-holding member is removed from the layer to provide the photovoltaic-element holding member.
(25) A method according to any one of the twelfth to twenty-fourth features (12) to (24), wherein the step of forming the light-transmitting layer comprises supplying the light-transmitting material to a container and thereby forming the light-transmitting layer.
In many cases, the light-transmitting layer is formed of a material in a liquid or half-solid state. Accordingly, the light-transmitting layer can be easily formed using the container.
Usually, the container is used for just forming the light-transmitting layer and is not used as part of the photovoltaic panel. Therefore, after the photovoltaic-element holding member is produced, or after the photovoltaic panel is produced, the container is removed. However, the container may be employed as part of the photovoltaic panel.
In the case where at least a portion of the container is formed of a light-transmitting material, that portion of the container need not be removed. That is, that portion of the container can be deemed as part of the light-transmitting layer, and a rigidity of the photovoltaic panel can be increased by that portion of the container.
In the case where the container is removed after the photovoltaic panel is produced, the container can be used to protect the light-transmitting layer during the production of the photovoltaic panel. As will be described in DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS, a portion of the container may be utilized as a stopper which defines a limit of movement of the temporarily holding member toward the container.
The container is not essentially needed to form the light-transmitting layer. For example, if the light-transmitting layer is formed of a material having a high viscosity, the container is not needed.
(26) A method according to any one of the twelfth to twenty-fifth features (12) to (25), wherein the step of forming the at least one electrode comprises forming two electrodes on one of opposite sides of the photovoltaic-element holding member.
(27) A method according to any one of the twelfth to twenty-fifth features (12) to (25), wherein the step of forming the at least one electrode comprises forming two electrodes on opposite sides of the photovoltaic-element holding member, respectively.
An electrode connected to respective P-type layers of the photovoltaic elements, and an electrode connected to respective N-type layers of the elements may be both provided on one of opposite sides of the photovoltaic-element holding member, or may be respectively provided on the opposite sides of the holding member. In the latter case, one electrode which is provided on one side of the holding member to which light is incident is formed to cover only a portion of the light receiving surface of the holding member so that the light is efficiently utilized by the photovoltaic elements, or is formed of a transparent material.